Isotopes of lawrencium

Key takeaways

Isotopes of lawrencium belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Isotopes of lawrencium to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Isotopes of lawrencium from memory before moving on to harder problems.

Reference excerpt

Lawrencium (103Lr) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was 258Lr in 1961. There are fourteen known isotopes from 251Lr to 266Lr, except 263Lr and 265Lr, and seven isomers. The longest-lived known isotope is 266Lr with a half-life of 11 hours.

List of isotopes

Nucleosynthesis

Cold fusion 205Tl(50Ti,xn)255−xLr (x=2) This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Evidence was provided for the formation of 253Lr in the 2n exit channel. In 2022, two states (253Lr and 253mLr) were found.

203Tl(50Ti,xn)253−xLr (x=2) This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. In 2022, two states (251Lr and 251mLr) were found.

208Pb(48Ti,pxn)255−xLr (x=1?) This reaction was reported in 1984 by Yuri Oganessian at the FLNR. The team was able to detect decays of 246Cf, a descendant of 254Lr.

208Pb(45Sc,xn)253−xLr This reaction was studied in a series of experiments in 1976 by Yuri Oganessian and his team at the FLNR. Results are not readily available.

209Bi(48Ca,xn)257−xLr (x=2) This reaction has been used to study the spectroscopic properties of 255Lr. The team at GANIL used the reaction in 2003 and the team at the FLNR used it between 2004–2006 to provide further information for the decay scheme of 255Lr. The work provided evidence for an isomeric level in 255Lr.

Hot fusion 243Am(18O,xn)261−xLr (x=5) This reaction was first studied in 1965 by the team at the FLNR. They were able to detect activity with a characteristic decay of 45 seconds, which was assigned to256Lr or 257Lr. Later work suggests an assignment to 256Lr. Further studies in 1968 produced an 8.35–8.60 MeV alpha activity with a half-life of 35 seconds. This activity was also initially assigned to 256Lr or 257Lr and later to solely 256Lr.

243Am(16O,xn)259−xLr (x=4) This reaction was studied in 1970 by the team at the FLNR. They were able to detect an 8.38 MeV alpha activity with a half-life of 20 s. This was assigned to 255Lr.

248Cm(15N,xn)263−xLr (x=3,4,5) This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to assign alpha activities to 260Lr, 259Lr and 258Lr from the 3-5n exit channels.

248Cm(18O,pxn)265−xLr (x=3,4) This reaction was studied in 1988 at the LBNL in order to examine the possibility of producing 262Lr and 261Lr without using the exotic 254Es target, and successfully accomplished this. After chemical purification of the Lr from the reaction, they were able to measure fission from 261Lr with an improved half-life of 44 minutes. The production cross-section was 700 pb; from this a 14% electron capture branch of 261mRf was calculated if this isotope had been produced via the 5n channel rather than the p4n channel. This is an upper limit, as it was determined that the p4n channel does occur. A lower bombarding energy (93 MeV instead of 97 MeV) was then used to measure the production of 262Lr in the p3n channel; as it was calculated that any electron capture of 262Rf should be negligible, the 4n channel was discounted. The isotope was successfully detected and a 240 pb cross-section measured. This detection of the p3n channel supported the p4n assignment for the lighter isotope. For neither was there any attempt to differentiate the SF and EC+SF decay modes.

246Cm(14N,xn)260−xLr (x=3?) This reaction was studied briefly in 1958 at the LBNL using an enriched 244Cm target (5% 246Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25 seconds. Later results suggest a tentative assignment to 257Lr from the 3n channel.

244Cm(14N,xn)258−xLr This reaction was studied briefly in 1958 at the LBNL using an enriched 244Cm target (5% 246Cm). They observed a ~9 MeV alpha activity with a half-life of ~0.25s. Later results suggest a tentative assignment to 257Lr from the 3n channel with the 246Cm component. No activities assigned to reaction with the 244Cm component have been reported.

249Bk(18O,αxn)263−xLr (x=3) This reaction was studied in 1971 by the team at the LBNL in their large study of lawrencium isotopes. They were able to detect an activity assigned to 260Lr. The reaction was further studied in 1988 to study the aqueous chemistry of lawrencium. A total of 23 alpha decays were measured for 260Lr, with a mean energy of 8.03 MeV and an improved half-life of 2.7 minutes. The calculated cross-section was 8.7 nb.

252Cf(11B,xn)263−xLr (x=5,7??) This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% 252Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to 257Lr. Later results suggest a reassignment to 258Lr, resulting from the 5n exit channel. The 8.4 MeV activity was also assigned to 257Lr. Later results suggest a reassignment to 256Lr. This is most likely from the 33% 250Cf component in the target rather than from the 7n channel. The 8.2 MeV was subsequently associated with nobelium.

252Cf(10B,xn)262−xLr (x=4,6) This reaction was first studied in 1961 at the University of California by Albert Ghiorso by using a californium target (52% 252Cf). They observed three alpha activities of 8.6, 8.4 and 8.2 MeV, with half-lives of about 8 and 15 seconds, respectively. The 8.6 MeV activity was tentatively assigned to 257Lr. Later results suggest a reassignment to 258Lr. The 8.4 MeV activity was also assigned to 257Lr. Later results suggest a reassignment to 256Lr. The 8.2 MeV was subsequently associated with nobelium.

250Cf(14N,αxn)260−xLr (x=3) This reaction was studied in 1971 at the LBNL. They were able to identify a 0.7s alpha activity with two alpha lines at 8.87 and 8.82 MeV. This was assigned to 257Lr.

249Cf(11B,xn)260−xLr (x=4) This reaction was first studied in 1970 at the LBNL in an attempt to study the aqueous chemistry of lawrencium. They were able to measure a Lr3+ activity. The reaction was repeated in 1976 at Oak Ridge and 26s 256Lr was confirmed by measurement of coincident X-rays.

249Cf(12C,pxn)260−xLr (x=2) This reaction was studied in 1971 by the team at the LBNL. They were able to detect an activity assigned to 258Lr from the p2n channel.

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Worked examples

Example 1 — a first encounter with Isotopes of lawrencium

Start with the simplest possible case. Write down what Isotopes of lawrencium claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Isotopes of lawrencium before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Isotopes of lawrencium ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Isotopes of lawrencium

In research: Isotopes of lawrencium appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Isotopes of lawrencium in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Isotopes of lawrencium is common in secondary-school and first-year university syllabi. It links to neighbouring topics Isotopes of lawrencium, Lawrencium, Lists of isotopes by element, so understanding it makes those chapters shorter.
In everyday life: Look for Isotopes of lawrencium outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Isotopes of lawrencium in 20 minutes

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Frequently asked questions

What is Isotopes of lawrencium in simple terms?

Lawrencium (103Lr) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes.

Why does Isotopes of lawrencium matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Isotopes of lawrencium?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Isotopes of lawrencium.